The present invention relates to a production counter for indicating the number of sheets of material automatically cut by a knife. In particular, the invention relates to a dynamic production counter for indicating the number of sheets of material actually cut by the knife of a corrugator as well as the number of sheets remaining to be cut before a production order is finished.
In a corrugator for producing paperboard, liner is fed to a single facer machine. A corrugating machine is also fed to the single facer machine. In the single facer machine, the corrugating medium is adhesively bonded to the liner to form a single faced web.
The single faced web is fed by a conveyor to the upper level of a bridge. Another single facer machine may be provided to produce a second single faced web which is transported by a second conveyor to the lower level of the bridge.
The singled faced web leaves the bridge along a bridge guide. The bridge guide feeds the single faced web through a preheater and glue machine to a double facer machine. The glue machine applies an adhesive bonding agent to the exposed crests of the flutes on the single faced web. The web is bonded to a liner fed to the double facer machine. The double facer machine maintains the single face web in contact with the liner while subjecting these components to controlled heat to gelatinize a starch solution used as an adhesive bonding agent.
The double faced web is fed to the slitter and scorer which determines the ultimate width of the paperboard to be produced as well as the lines along which it may be folded. The web is then fed to rotary cutting knives for severence into sheets of predetermined lengths.
The lay-out of a corrugator combining the above components is described in detail in application Ser. No. 369,632 entitled "Corrugator" filed June 13, 1973 incorporated herein by reference.
A measuring wheel senses the speed of travel of the double faced web and generates a stream of pulses in response thereto. In addition, the measuring wheel is used to generate a stable singal to indicate that double faced web is present at the double facer machine output. The rotation of the cutting knives is sensed by a magnetic pick-up or the like which generates a stream of knife pulses indicative of the sheets cut by the knives. Each knife pulse represents one sheet of web material. The measuring wheel and knife pick-up are substantially as described in U.S. Pat. No. 3,411,388; and entitled "Integrated Sheet Production Control System" issued to Rappaport on Nov. 19, 1968.
Heretofore, to provide a count of the number of sheets of web material cut by the knives in a corrugator, it was necessary to use two or more sets of counters or two or more sets of comparators. A system using two or more sets of counters is described in U.S. Pat. No. 3,411,388. A production counter is preset to the production order, that is, the predetermined number of sheets of web material to be cut by the knives. The knife pulses are used to count down the production counter. The production count, that is, the number of sheets actually cut by the knives, is not tracked directly by the counter. Instead, the contents of the counter indicate the number of sheets of material remaining to be cut to complete the production order. The stages of the counter are hardwired to a detection circuit to provide an indication of a limited number of warning levels. Each warning level represents a predetermined number of sheets to be cut to fill the production order. If a five stage counter is used, the warning levels indicate one, ten, one hundred, one thousand or ten thousand sheets remaining to be cut. The warning levels are fixed by the system wiring.
The correction of the production count for scrap sheets takes place at the pulse repetition frequency of the knife pulses. As a result, if the number of scrap sheets is incorrectly estimated, the scrap count cannot be revised instantaneously.
The number of scrap sheets cut by the knives are observed by the operator. The operator estimates the number of scrap sheets and presets a scrap counter to that number. To correct for the scrap sheets, the production count is halted by temporarily disconnecting the production counter from the knife pulse line. The knife pulses are transferred to the scrap counter which counts down from the preset count to zero. When the scrap counter reaches zero, the production count is resumed by transferring the knife pulses back to the production counter. The scrap counter is disconnected from the knife pulse line. Thus, the scrap counter must first be counted down at the knife pulse rate to zero before an incorrect scrap estimate can be corrected by the operator.
It is also known in the art to use a single production counter for providing an indication of the number of sheets of web material remaining to be cut. The counter is operated by the knife pulses as previously described. The output of the counter, however, is fed to two comparators. The use of two comparators significantly increases the equipments costs.
Each comparator is associated with a separate set of thumb wheel switches. One set of thumb wheel switches is preset to the production order. The other set of thumb wheel switches indicates the complement of a preselected warning level rather than the warning level itself. Thus, the switches are set to the actual number of sheets cut, rather than the number of sheets remaining to be cut, at the time the warning is to be provided to the operator. When the output of the production counter coincides with one of the thumb wheel settings, the associated comparator provides an output signal. If the thumb wheel setting for the production order is changed, the thumb wheel setting for the complement of the preselected warning level must also be changed. Thus, the warning level setting must be changed between changes in production orders.
The present invention provides a selectable warning level, virtually instanteous correction of the production count for scrap sheets, the ability to revise the estimated correction for scrap material without interrupting the production count, the elimination of multiple comparator controls, and the ability to change production orders without re-adjusting the warning level.
Applications of the invention are universal. The invention need not be limited to use in a corrugator. The invention can be used to provide a count of any type of repetitive events, including an indication of the number of such events required to occur before a predetermined count is reached.